I have a 94 sport with a 318. when i start the truck up i can hear a definite "sucking noise". all the vacuum lines are hooked up so im thinking it could be a gasket thats blown. Its also running extremly rich. I want to hear some opinions on this problem. thanks in advance.

 

It could be anything from a hose to like you said a bad gasket. The IAC Idle Air Control motor can make that noise as the needle is moved. Take off the air cleaner and check the Throttle Body.